The identification and subsequent measurement of source and load impedances are useful tools for assessing and evaluating stability of electrical power systems. The impedance of an alternating current (AC) electrical system may be measured by injecting a perturbation signal in the direct and quadrature (dq) reference frame of the system, and measuring the voltage and current response to the perturbation.
Conventionally, impedances of a system at AC interfaces have been extracted in the direct and quadrature (dq) reference frame using only shunt injection. Problems arise in such conventional impedance measurement methods because the source impedance is usually much smaller than the load impedance at AC interfaces. When perturbing the system using shunt mode, most of the injected current flows into the low impedance source side. The high impedance load side is not disturbed enough, resulting in a low signal-to-noise ratio (SNR) which is not good for measurement accuracy. Further, conventional approaches have generally been limited to linear loads and are not well-adapted for non-linear loads.
Therefore, there is a need for a system and method capable of realizing improved load-side SNR and overall impedance measurement accuracy.